This is awful. Just plain awful.

The logic of this makes no sense. Scooby clearly demonstrates basic intelligence and sentience throughout every official iteration of the show. Combined with cartoon logic, he would likely just comically zoom out of there once he realizes that he can indeed operate door handles, or that there is some sort of Scooby snack or STACKED sandwich somewhere outside. So even if there would be a joke about Scooby realizing he doesn’t have the opposable thumbs to operate the door handles (even though dogs IRL have demonstrated they can open more complex door handles, latches, and other mechanisms,) Scooby could also just punch a Scooby-sized hole in the van to get to his prized hobby of eating.

A far more realistic “dark” take would be something akin to who made Scooby sick by feeding him so much food that’s bad for dogs, though again I’d argue he’s demonstrated an iron stomach.